Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$238.48	10.735%	$264.0808	$264.08	$264.10	$264.10
Purchase #2	$127.38	11.431%	$141.9408	$141.94	$141.95	$141.90
Purchase #3	$32.33	6.749%	$34.512	$34.51	$34.50	$34.50
Purchase #4	$65.63	3.270%	$67.7761	$67.78	$67.80	$67.80
Purchase #5	$198.99	13.532%	$225.9173	$225.92	$225.90	$225.90
Purchase #6	$172.92	4.780%	$181.1856	$181.19	$181.20	$181.20
Purchase #7	$107.85	3.772%	$111.9181	$111.92	$111.90	$111.90
7 purchase totals =	$943.58		$1,027.3307	$1,027.34	$1,027.35	$1,027.30